Handling aircraft fuel must be done according to local airport safety regulations and rules. If not done properly the results can be really devastating to you and others. Aircraft fuel is highly combustible and burning AVgas is only useful to us inside an engine while trying to rotate the propeller. Here we are going to discuss safety practices everybody should adhere too.
Contaminated or the wrong type of fuel can be a recipe for an off airport landing, below you will find some procedures to test for water, alcohol and the fuel color.
Before the first flight of the day and after refueling (let the fuel settle first before testing so that any impurities will sink down) it is wise to see with a fuel tester if water or debris is in the tanks or engine gascolator. Do this with one of the samplers shown and drain the fuel tanks and fuel system at the lowest point. It is best to start at the tanks and work your way to the lowest point (usually the gascolator near the engine). This avoids water in the tanks being drawn into the fuel lines. See the POH for exact details of your aircraft.
Know how many drain points your aircraft has and after draining make sure the drain valve closes properly and does not keep on leaking fuel. And while you are at it: check the fuel tank vents for blockage.
Some have asked how water gets into a fuel tank. There are several reasons for that:
What to do with drained fuel that is clean? Well, I put it back in the fuel tank. You just concluded that fuel in the sample cup (which should be squeaky clean) is clean so the fuel in the tank must be too. Why not put it back then if then fuel in the sample cup is clean? If you will not trust the clean fuel in the cup why trust the fuel in the tank which you can not see anyway?
If it is contaminated, or if you are not sure about it, then put it in a separate container (clearly marked as contaminated) and use it for maybe a lawnmower or your car. Do not pour it on the platform or in the grass, if not sure, ask the FBO or airport operator what to do with drained fuel.
Another option is to save the drained fuel in a specially marked container and when its full pour it back in the aircraft through a special filter like Mr. Funnel.
As mentioned previously, aviation fuel is dyed with a specific color to distinguish the separate ratings. Below you can see which colors are used:
| Fuel grade | Color | Usage | Comments |
| AVgas 100/130 | Green | Most light piston engine aircraft | Will cause spark plug fouling due to high lead content |
| AVgas 100LL | Blue | Most light piston engine aircraft | Lower lead version of above |
| AVgas 82 UL | Purple | Most light piston engine aircraft | No lead version of above |
| JET A/A1 | Straw or clear | Turbine/ Diesel aircraft | Distinctive smell, not to be used in spark ignition engines |
| Diesel/Biodiesel | Clear | Diesel aircraft | Distinctive smell, not to be used in spark ignition engines |
| AG Diesel | Red | Diesel aircraft | Distinctive smell, not to be used in spark ignition engines |
When sampling, hold the container against a white background to verify the color, a sheet of white paper or against the wing (if its painted white) will do fine.
The following steps describe how to test if there is any alcohol in your Mogas:
Interpreting the above test:
Operators of aircraft approved for operation with Mogas containing methanol or ethanol shall consider the lower energy content of such a fuel (which will result in a lower performance or higher fuel consumption).
